1. Field of the Invention
This invention relates to a function setting method for an audio system which is constructed such that sources incorporated therein are controlled in a concentrated manner by a system controller.
2. Description of the Prior Art
An audio system, for example, of the car-carried type is normally constructed such that a plurality of audio sources, such as a compact disk player, a cassette tape deck, a radio set and a clock are incorporated in an integrated relationship as a system therein. Those sources are controlled in a concentrated manner by a system controller which may be, for example, in the form of a microcomputer.
The functions of an audio system, for example, the types and number of sources to be combined, are variously different depending upon grades or points of destination (for domestic use, for abroad and so forth) of products, and products must be manufactured in accordance with such functions. Conventionally, in order to change such functions, it is a common practice to replace a microcomputer serving as a system controller with another microcomputer in which control programs conforming to object component sources are built or to make use of a function setting circuit additionally provided for a microcomputer serving as a system controller.
An exemplary one of the above-described conventional audio systems which employ a function setting circuit in addition to a microcomputer serving as a system controller is shown in FIG. 4. Referring to FIG. 4, with the audio system shown, control programs for all functions of the audio system are built in advance in a microcomputer 41 serving as a system controller for the audio system, and connection of diode pairs in a function setting circuit 42 is changed to select a control program or programs corresponding to a desired function or functions from among the built-in programs. For example, where diode pairs 43, 44 and 45 in the function changing circuit 42 are individually connected to such positions as shown in FIG. 4, if a power source for the audio system is switched on, then a ground potential, that is, 0 volt, is supplied for a fixed period of time to a data scan terminal KS5 of the microcomputer 41 from the function setting circuit 42. Data input terminals KR0, KR1 and KR3 are connected to the data scan terminal KS5 by way of diode parts 43, 44 and 45, respectively, while only a data input terminal KR2 is not connected to the data scan terminal KS5. Accordingly, when a ground potential is supplied to the data scan terminal KS5 as described above, function setting data "0010", corresponding to the connection of the diode pairs shown in FIG. 4, are taken into the microcomputer 41 by way of the data input terminals KR0 to KR3. The data "0010" here are determined in advance such that they correspond to a certain function to be set, and a control program for the function corresponding to the data "0010" is selected from among the control programs built in the microcomputer 41 to perform setting of a function of the object. In order to change a function to be set, connection of the diode pairs in the function setting circuit 42 should be changed corresponding to a desired function to be set. Since the four data input terminals KR0 to KR3 are used as data input terminals in the circuit shown in FIG. 4, a total of 16 functions corresponding to function setting data "0000" to "1111" can be set with the audio system.
It is to be noted that the reason why the diode pairs 43 to 45 are used for setting of a function in FIG. 4 is that it is intended to prevent a possible roundabout of a ground potential from such commonly connected other circuits because not only the function setting circuit 42 described above but also, for example, a key matrix circuit 46 provided on a key input panel are connected commonly to the data input terminals KR0 to KR3.
While setting of a function is performed in such a manner as described above with the conventional audio system shown in FIG. 4, in order to effect changing of a function, alteration of hardware of the system controller must be performed such that a number of different microcomputers corresponding to the number of functions to be changed are prepared or that the connection of the diodes of the function setting circuit of the system controller is changed in accordance with a function or functions to be newly obtained.